(1) Field of the Invention
The present invention pertains to an auto-pull follower apparatus used in a grease gun having a grease reservoir with a follower piston mounted for reciprocating movement therein, where the follower piston is moved in a first direction through the interior of the reservoir to enable loading grease into the reservoir interior or to increase the interior volume of the reservoir to permit insertion of a grease containing cartridge or collapsible container, and where the follower piston is moved by a piston spring in the opposite direction through the reservoir to move loaded grease from the reservoir interior or from a grease cartridge or container contained in the interior to a pump of the grease gun. The reciprocating piston is provided with a novel autopull mechanism comprising a spring biased spool mounted for rotation on the piston, and a flexible cord or chain extending from the spool and out of the reservoir through a hole in a rearward end wall of the reservoir. Pulling the end of the cord outside the reservoir causes the spool to rotate against the bias of the spool spring and a length of cord to be unwound from the spool, and then causes the piston to move against the bias of the piston spring in a direction towards the reservoir end wall. The movement of the piston toward the end wall increases the interior volume of the reservoir and enables the loading of grease into the reservoir interior. Releasing the cord causes the spring bias of the spool to automatically retract the length of cord pulled from the reservoir back into the reservoir interior and rewinds the length of cord back on the spool.
(2) Description of the Related Art
Manually operated high pressure grease guns commonly comprise a dispensing pipe, a pump housing, and a tubular grease supply reservoir removably attached to the pump housing. The dispensing pipe commonly has a nozzle fitting at one end for dispensing grease pumped from the gun. The opposite end of the pipe communicates with a manually operated pump contained in the pump housing. The pump is operated by a manual lever mechanism pivotally connected to the pump housing. Manipulating the lever mechanism dispenses grease contained in the supply reservoir of the gun through the dispensing pipe.
The tubular grease supply reservoir is removably attached to a threaded grease supply opening of the pump housing by a series of screw threads provided at an open end of the reservoir. A piston is mounted for reciprocating movement in the reservoir interior. The piston is biased by a piston spring toward the open end of the reservoir connected to the grease supply opening of the pump housing. Movement of the piston toward the reservoir open end by the piston spring moves grease from the reservoir interior to a pump intake and automatically decreases the volume of the reservoir interior as grease is dispensed from the gun.
To load the grease supply reservoir with grease, the operator of the gun first unscrews the tubular reservoir from the grease supply opening of the pump housing, and retracts the piston in the reservoir interior against the bias of the piston spring. The piston is typically retracted in the reservoir interior by a rod that is connected to a rearward face of the piston and extends out of a rear end wall of the tubular reservoir. The end of the rod extending outside the reservoir is pulled away from the reservoir end wall, causing a length of rod to be pulled from the reservoir interior through the reservoir end wall. Pulling the rod from the reservoir also causes the piston attached to the opposite end of the rod to slide toward the end wall in the reservoir interior against the bias of the piston spring. Grease in bulk is then packed in the open end of the tubular reservoir or an open ended grease cartridge is inserted into the reservoir interior. The operator then reassembles the reservoir to the pump housing by screwing the reservoir open end into the grease supply opening of the pump housing. The rod is then reinserted back into the reservoir. The rod is connected by a sliding connection to the piston so that as the rod is pushed back into the reservoir, the piston stays in substantially its retracted position and the rod is inserted into the grease in front of the piston. The grease gun is now ready for use.
Grease guns of the type described above are designed for use with grease packed in bulk in the reservoir interior or with open ended grease cartridges inserted into the reservoir interior. This is so because once the pull rod connected to the piston in the reservoir interior is retracted out the end wall of the reservoir to permit loading of grease or an open ended grease cartridge into the reservoir interior, the pull rod must then be reinserted back into the reservoir interior through the end wall. The grease contained in the reservoir interior or in the grease cartridge inserted in the interior enables the rod to pass through the grease as it is reinserted into the reservoir interior.
Grease guns of the type described above are not capable of using a collapsible grease container inserted into the reservoir interior because the collapsible container prevents the pull rod from being reinserted back into the reservoir interior after it has been pulled from the reservoir to reposition the spring biased piston at the rearward end of the reservoir. Attempting to reinsert the rod into the reservoir interior is prevented by the end of the rod inside the reservoir engaging against the collapsible container.
What is needed to overcome this disadvantage of known grease guns and to provide a high pressure grease gun that may be used with grease in bulk, grease contained in open ended cartridges, as well as grease contained in a collapsible container, is a spring biased piston in the reservoir interior that is retracted through the interior to permit the loading of grease therein, but does not require a pull rod that extends from the rearward end of the reservoir when the piston is retracted in the reservoir, and is reinserted into the reservoir interior after the interior has been loaded with grease.
The present invention overcomes the disadvantages associated with known grease guns set forth above by providing an auto-pull follower device having a flexible cord that is pulled from the rearward end of the grease supply reservoir to retract the spring biased piston in the reservoir for loading grease, and having a spring biased spool connected to the flexible cord that automatically retracts the length of cord pulled from the rearward end of the reservoir back into the reservoir interior and rewinds the length of cord on the spool.